Generally, a vehicle is provided with various kinds of convenience devices for improving the convenience of a driver or a passenger. A power seat is an example of such convenience devices. The power seat in the above description allows a specific driver to let the seat position memorized in advance in accordance with his/her body type so that the seat position can be adjusted to a previously remembered seat position by simply operating the memory replay button thereafter. Namely, the power seat has an advantage that the current seat position can be conveniently adjusted to the previously memorized seat position by pressing the memory reproduction button once without needing to newly adjust the different seat position according to the driver.
The power seat needs to detect the number of revolutions of the motor to control the position. For this, a ring magnet, a reed switch, or a Hall sensor that rotates together with the rotation axis of the motor is used. And the motor only controls the position of the power seat in the power seat control unit by counting the pulse waveform generated from the hall sensor or the reed switch.
Meanwhile, when the power seat is moved to the end of the sliding movement, the seat is pinched by the structure. When the seat is pinched, the seat movement is not normally performed even if the switch is operated.
Accordingly, a method to limit the stroke of the seat operation is applied. Namely, a Limit switch or a Stopper which mechanically performs forced restriction is used for the seat mechanism. However, since the Limit switch is relatively expensive, it causes a rise of manufacturing cost. And in the case of the stopper, there is a problem that the durability of the power seat is deteriorated due to damage to the motor and the seat mechanism when the forced restraint repeatedly occurs for a long period of time and a problem that the passenger is dissatisfied with the impact caused by the forced restraint.
Therefore, as an alternative method, controlling the region (stroke) of the seat operation by using the pulse signal of the motor has been suggested. Namely, the length of the track along which the power seat moves is detected by using the pulse signal of the motor and the motor device is stopped before the power seat reaches both ends of the track. At this time, the virtual limit section along which the power seat will practically move is determined.
FIG. 1 is a drawing illustrating the virtual limit section of the power seat.
In FIG. 1, two virtual limit points are set so that the seat does not move to both ends of the track. Accordingly, a virtual limit section (a) is provided, and the power seat slides within the virtual limit section (a). Of course, when the operation switch is inputted a predetermined number of times or more at the virtual limit point, the power seat can move to the physical limit of the track. Namely, if the operation switch is continuously operated, it moves beyond the remembered virtual limit point and moves to the actual end.
However, even if the virtual limit is set as described above, the power seat may be hard-stopped within the virtual limit section or beyond the virtual limit section. At this time, the control unit initializes the virtual limit setting information.
When the setting information for the virtual limit is initialized as described above, the control unit cannot normally operate the power seat due to the lack of information on the virtual limit. In this case, it is troublesome for the user to newly set the virtual limit.
Of course, when a hard stop occurs as described above, the control unit also corrects the virtual limit position.
The position correction corrects for a predetermined distance inward from the initially set virtual limit point as shown in FIG. 2. At this time, the correction point is located inside the virtual limit point.
However, when the position correction is performed in such a manner, there can be a problem that the operation section of the power seat becomes shorter and shorter.